Metal having two coats of sulfurcontaining nickel and method of making same



3,183,067 Patented May 11, 1965 United States Patent Oflice METAL HAVING TWO COATS OF SULFUR- CONTAINING NICKEL AND METHOD OF MAKING SAME Arthur H. Du Rose, Euclid, and Robert L. Stern, Cleveland Heights, Ohio, assignors to The Harshnw Chemical Company, Cleveland, Ohio, a corporation of Ohio N'o Drawing. Filed Dec. 6, 1961, Ser. No. 157,556

13 Claims. (Cl. 29-194) This invention relates to corrosion resistant composite metallic articles and to electrodeposition methods of producing said articles.

Considerable effort has'been devoted to the production 1 of corrosion resistant platedmetallic articles and-particularly to corrosion resistant nickel plated articles. Nickel is especially suitable for corrosion prevention in that it forms coatings which are more'or less of a permanent white appearance and possess a high degree of resistance to corrosion by natural waters, sea water and alkaline and salt solutions. Nickel coatings, however, are also subject to corrosion due to certain phenomena existing in the structure of the coating and in the relation existing between the various components of the coated article.

In recent years improved corrosion protection of decorative deposits has been obtained through the use of duplex" nickel coatings. Duplex nickel coating may generally be defined as two layers of nickel deposited directly-without an intermediate layer-on one another from two different electrolytes. .The two layers are generally a bright nickel layer superimposed over a semibright nickel layer. "Examples of duplex baths may be found in US. Patent No. 2,879,211 and British Patent Metals coated with the correct combination of duplex nickel deposits have been found to give increased corrosion protection, both under accelerated test conditions and under ordinary usage. The uniformity of resistance to corrosion, however, has been found to vary. Inability to remove variations in corrosion resistance has been prisistant duplex nickel coated articles may be obtained by controlling the amounts of sulfur contained in both of the nickel coatings making up the duplex deposit. Sulfur in nickel deposits is derived from the sulfo-oxygen control agents and the amount thus derived is increased by the presence of so-called brighteners even when the latter does not contain sulfur. Sulfur in even higher percentages may be obtained by the use of brighteners containing sulfur, such as, for instance, thiourea, diethyl thiourea and isothioureadipropionic acid. The corrosion resistant article of this invention may have as a basis metal any metal which is subject to atmospheric corrosion. Preferably, the basic metal is a metal selected from the group consisting of aluminum, iron, copper and zinc and alloys thereof coated with two superimposed coats of sulfur-containing nickel, said nickel coatings containing different amounts of sulfur such that the top nickel layer is not less than 60 mv.

more electronegative and preferably not less than my. more electronegative than the nickel layer nearest-the basis metal. Preferably the corrosion resistant article of this invention has a chromium layer superimposed on the top nickel layer. The electronegativity of the nickel layers is determined in a manner which is described hereinafter.

The sulfur content of normal bright nickels from solutions which contain both control agent and brightener is from about 0.045% to about 0.15%. The bright nickel is the top coating in a duplex nickel deposit. The semibright deposit from the same solution without the brightener may contain 0.015% to 0.04% sulfur. The semibright nickel is the coating underneath the bright nickel in a duplex deposit. The sulfur content of the semi-bright deposit can be reducedbyf using less control agent. The sulfur content in the bright nickel deposit can be increased by use of more control agent and a brightener. By one or both of these methods it is possible to obtain the potential difference desired.

Almost without exception the first or underlying layer of nickel will be deposited from a solution, Watts or otherwise, which contains a low concentration of sulfa-oxygen control agent and no brightener. The second or top layer of nickel will be from-a solution which contains a normal to high concentration of carrier plus a brightener. The

first layer of ductile semi-bright nickel is the thicker of l thinner than the first, being from about 0.05 to about 0.5 7

mil thick. When a chromium. layer is superimposed over the second nickel layer, a chromium layer about 0:01 mil thickis employed.

Since the analysis of sulfur in nickel deposits is difiicult compared to the measurement of potentials, the difference between the two layers of nickel is defined in terms of potential difference instead of sulfur-content difference.

The duplex deposits are described in terms of potential difference taken in a specific solutioni The potential difference is referred to in the following tables as AB in millivolts. Potential measurements are taken in an aqueous solution of 3 g. of NaCl and .02 g. of Cu(NO);) .-3H;O per ml. of water adjusted with hydrochloric acid to a pH of 3.0 and at room temperature. The procedure is to measure the potential of the deposit versus a saturated calomel electrode. The potential of a low sulfur-content nickel deposit versus the saturated calomel electrode will vary between --90 and mv. The potential for the case of the top layer which contains more sulfur (and usually a brightener) will vary from to 200 mv. The higher the value (or the more electronegative), the greater is the tendency of that deposit to corrode. It is essential that the top layer of nickel be. relatively less resistant to corrosion than the first layer. Table -I gives the potential difference between types of deposits, and the relative corrosion rating for 1.25 mil total nickel (1 mil first layer plus 0.25 mil second layer) on steel. The corrosion test carried out in Table I was the Corrodkote test. Chrome thickness was 0.01 mil.

TABLE I SOLUTIONS USEDIN TABLE I-Continued m Watts. Corrodkote Nickel naphthalene disnltonate g./l 6 w g), 2/1.... 0. 02 Solution Solution AE in Corrosion Combination (or first for second millirating Temperature "i F" layer layer volts 5 Current density .4111... 40 (n) watg' bi (dib it mid /l p,px senzenesu on e g. .0 a 3g g- Tlliiodigropionltrile g./l 0.0 0 2 p d b 60 Temperature F-.. 135 e b Current densit a.s.t.. 40 f b 80 Very good. 10 g 1 70- Do. (0) Nickel chloride g./l..- 300 h n 75 Do. Nickel sulfate g./l 80 d l 60 Good. Boric acid g /l 30 i b 55 Poor. Saccharin g /l 3 j m 30 Do. EH 3.0 k b 20 Very poor emperature 100 h o 65 00d. Current density 150 n 1| 0 Very poor. p) watts Very o-Sulfobenzaldehyde 1 3 Na hthalene disulfonic acid g./i 2 SOLUTIONS USED IN TABLE I Th oureo. n 0.15 (a) li i bi h n I if n l) 44'bi h ldi nlt perature I F e Si] O en 8 one 8 p y y p y 5 Current density a.s.t.. 45

l 0 1 23;531:322 1 11- 120 C rw k te is the name given to an accelerated test m P which a synthetic road soil slurry is applied to the plated (1)) Watts. I surface of an article and the article then exposed to-a y, g g fii 3'0 \varm humid atmosphere. A Corrodkote slurry formulaguchsin d it Q 1%-- 0.005 25 non usually includes both soluble and insoluble elements ggggf g f fa 28 and suflicient liquid to give proper spreading consistency. pH I 3.8 The slurry is applied to the surface being tested by 0 Watts, means of a paint brush, or similar device, to produce a Nfiimlhgis (phenylsulf0nyl)-4,4 -biphenyldisglfon- 0 01 fairly uniform coating, after which the coated specimen Conmarin v 1.1 0.1 30 is exposed to specified humidity conditions. gg ifg 'i ff i::::::::::- gi- 32 A standard Corrodkote mixture, effective in testing pH 1 '1 chromium-nickel combinations over steel, is:

11 Watts.

N,N bis (phenylsulfonyl)-4,4'-biphenyldisulfong 30 F 31111611211 (3) p 4 8% 35 Ferric chloride g- 0.165

0 a CC. Current density i 40 C pnc nitrate 8 0935 Temperature 135 Ammonium chloride g.. l P Water -.ml 50 (6) 333. 005 Table 11 gives the potential difference between types of EH t a 4.0 40 deposits and the relative corrosion rating for 1.25 mil m Watts on steel. The corrosion test carried out in Table'n was Nickel fornmte 15 15 months atmospheric exposure. Chrome thickness was gobaltllsulfie7 3 0 01 mi] orma n 0.8 SiiIcclmrin 0 TABLE II n Y Temperature 165 Atmospheric exposure Current density a.s.f 60

(i1) Wflttfl- Solution Bolution AEin Relative gigs}. S335: :::"--""::::::::::fi: Combination for First torsecond milllvolts Corrosion Formalin (37%) c./l 0.8 Snccharin I g /lemperature 165 2 :8 g' Current densityd c 80 very Good (h) Nickel chloride g./l 300 e c G Nickel sulfate g./l 30 a c Fair- Boric acid g /l 30 It 0 75 Do. Saccharin g L- 0.5 a 4 60 1 3.0 f i 30 Poor. Temperature F-.. j k in D0 Current density a.s.f 150 i 2 W E (1') Watts.

N,N bis (phenylsulfonyl)-4,4'-biphenyldisulfon- 3 :3 3 5% 8% 60 (a) W H sonn'rrous USED IN TABLE II 8. S. gg F" 53 ug 21s w y sul yn-4,4'-bipheuymn 1ron- 0 1 Current density a.s.f 40 coumarm g 0 iii i i bib 1 di 1r t ggnent density Q 363 a e 3;; 65 Temperature 333:::::::::::::::::::: r: emp rature F watts (k) $355 density 50 Mag 21s (nhenylsulfonyl)-4,4'-biphenyidisgltonpi i'Diy-bis-(dibenzenesulfonamide) g./l 3g gg p p n emperature F 140 Current density Current density a,s f 50 70 Temperature (n r ri bi n 1 it I (c) watts ,aml-de s (p eny su onyl)-4,4 -biphenyldisgl; mq N, I;J 2is (phenylsultonyl)-4,4'-blphenyldiaulfonu Q.

Etlf diol g./1 2% g l iodipropionitrile ./l 0.0 05 Temperature 31": 140 Current densit Current density a. t- 50 75 Temperature f.- LIIIIIIIIIZ I 12?) SOLU'IIONSZ' USED IN TABLE IICntlnued (d) Watts.

Nickel formats ....g./l 15 y Cobalt sulfate g/ 3 Formalin (37%) .4 cc. 1.. 0.8 Saccharln g /1 0.02 H 2.3 ut-rent density 7 a s f 60 Temperature F-.. 165

(6) Watts.

Nickel formate g. /l 1 Cobalt sulfate g./l Formnlin (37%)v ..-cc./l 0. Saccharin g./l 0. .DH 2

Current density a s.f 6 v Temperature F 16 (.1) Watts.

N,N' bis (phenylsulfonyl)4,4'-blphenyldisulfonamide Q 0.1 Formalin (37%) ..cc /l 0.5 pH 3.8 Current density a.s.f 40 Temperature F 135 (9) Watts.

N,N' bis (phenylsulfonyl)-4,4-blphenyldisulfonamide Q /l 0.01 Coumarln g /l d 0.2 H 3.8 lurrent' density a s.f 60 Temperature F 130 (h) Watts.

N,N' bis (phenylsulfonyl)-4,4'-blphenyldlsulfonamide g furrent density a.s.f 40 Temperature F... 135 m wag-t0 bi (db 1f mid g/l 6 pp xys- 1 enzenesu ona e Fuchsln g /I 0.030% D I Current density a.s... 50 Temperature F... 135

0) w ts.

N i ckel naphthalene dlsulfonate g./l iurrent: density a.s.f 40 Temperature F..- 135 (k) Wwtts.

Nickel naphthalene disulfonate g./l 10 $602 a /l 0.05 H 2.5 urrent density a.s.f 60 Temperature F 135 (1) Watts.

Nickel naphthalene disulfonate g./l 10 Fuchsin /l.. 0.005 PH 2.5 Current density n s f 50 Temperature F-.. 135

Having thus disclosed our invention, what we claim is:

1. A method of making a duplex nickel coated corrosion resistant body comprising electrodepositing nickel upon a metal body from an aqueous, acid bath containing in addition to water, a nickel compound supplying nickel ions and a compound of the class consisting of organic sulfonates, sulfonamides and sulfimides, the concentration of said last mentioned compound added to said bath'being suflicient to cause deposition of sulfur as a part of said deposit; and depositing a second layer of nickel upon said first layer from an aqueous, acid nickel bath containing, in addition to water and a nickel compound supplying nickel ions a compound from the class consisting or organic sulfonates, sulfonamides and sulfimides, and a brightener compound, the concentrations of said two last mentioned compounds being such as to produce a second deposit over said first deposit at least 60 mv. more electronegative than said first electrodeposit.

2. The method according to claim 1 wherein said organic sulfonates, sulfonamides and sulfimides are aromatic sulfonates, sulfonamides and sulfimides.

3. In a method of making a duplex nickel coated corrosion resistant body comprising a lower layer of nickel and an upper layer of nickel adjacently bonded thereto wherein said upper layer of nickel is more anodic than said lower layer of nickel because of the presence of relatively more sulfur in said upper layer of nickel than in said lower layer of nickel, said method comprising electrodepositing upon a metal body said lower layer of nickel from an aqueous acid bath maintained at a pH between 2 and 4 containing a nickel-supplying compound and a sulfur-supplying compound at a current density in the 6' range of from about 40 amperes per square foot to about 150 amperes per square foot and at atemperature in-the range of from about 100 F. to about 165 F., and wherein the potential of said deposit is determined in an electrolyte comprising an aqueous solution of 3 grams of sodium chloride and .02 gram of Cu(NO .3H O per 100 mls. of water adjusted to a pH of 3.0 and at room temperature; and depositing said upper layer of nickel uponf'said lower layer of nickel from a similar bath containing a brightener compound wherein said deposit has a potential as measured of at least millivolts more anodicthan said lower layer of nickel. 1

4. A process for preparing'a coating system comprising a first layer of sulfur-containingsemi-bright nickel and a second layer of sulfur'containing bright nickel said process including the steps of electrodepositing 'froma nickel electroplating bath said first layer of nickel containing from about 0.007 percent to about 0.03 percent by weight sulfur and electrodepositing a second layer of bright nickel directly on the surfaceof said first layer of nickel to form a nickel layer containing from about 0.06 percent to about 0.30 percent by weight sulfur; and wherein said second layer of nickel contains sufficiently high concen tration of sulfur so that it is at least 60 millivolts more anodic than said first layer of nickel as determined by measuring the relative potentials of said nickel layers in an aqueous solution of 3 g. of sodium chloride and .02 g. of Cu(NQ .3H O. per 100'mls. of water at a pH of 3.0 at room temperature.

5. A process for preparing a coating system comprising a first layer of sulfur-containing semi-bright nickel and-a second layer of sulfufi-containing bright nickel said. process including the steps of electrodepositing from a first nickel electroplating bath a first nickel layer having a sulfur concentration in the range of from about 0.007 percent to about 0.03 percentby weight sulfur said first bath having been used to deposit under similar conditions a layer of nickel which was tested at room temperature for its potential versus a calornel half cell in an electrolyte solution of 3 g. of NaCl and .02 g. of Cu(NO .3H O per 100 mls. of water at a pH of 3.0, electrodepositing from a sec ond nickel electroplating bath a second layer of nickel containing from about 0.06 percent to about 0.30 percent by weight sulfur said second bath having been used to deposit a layer of nickel which was measured for its potential in an electrolyte solution containing the same ingredients and conditions as above, and wherein the potential for said second layer is at least 60 millivolts more anodic than the potential measurement for said first layer of nickel.

6. A process for the electrolytic preparation of a corrosion resistant article comprising electrodeposi-ting from an aqueous, acid, nickel plating solution on a basis metal of the type ,which is subject to atmospheric corrosion two superimposed layers of sulfur-containing nickel, said nickel layers containing difierent amounts of sulfur such that the top nickel layer is not less than 60 mv. more electronegative than the underlying nickel layer, s'aid electronegativity being determined from potential measurements taken in a solution of 3 g. of NaCl and .02 g. of

per mls. of wate'i' 'at a pH of 3.0 at room tempera- 1 9. The process of claim 6 wherein said top nickel layer is from about .05 to about 0.5 mil thick and said underlying nickel layer is from about 0.5 to about 2.0 mils thick.

10. A corrosion resistant article comprising a basis metal of the type which is subject to atmospheric corrosion coated with two superimposed coats of sulfur containing nickel, said nickel coatings containing different amounts of sulfur such that the top nickel layer is not less than 60 mv. more electronegative than the underlying nickel layer, said electronegativity being determined from potential measurements taken in a solution of 3 g. of NaCl and .02 g. of Cu(NO .3l-I,O per 100 mls. of water at a pH of 3.0 at room temperature.

11. The corrosion resistant article of claim 10 wherein the basis metal is a metal selected from the group consisting of aluminum, iron, copper and zinc and alloys thereof.

12. The corrosion resistant article of claim 10 wherein 8. said top nickel layer contains from about 0.06 to about 0.30 percent by weight sulfur, and said underlying nickel layer contains from about 0.007 percent to about 0.03 percent by weight of sulfur.

13. The corrosion resistant article of claim 10 wherein said top nickel layer is chromium plated.

References Cited by the Examiner UNITED STATES PATENTS 3,090,733 5/63 Brown 204-40 JOHN H. MACK, Primary Examiner. MURRAY TILLMAN, Examiner. 

3. IN A METHOD OF MAKING A DUPLEX NICKEL COATED CORROSION RESISTANT BODY COMPRISING A LOWER LAYER OF NICKEL AND AN UPPER LAYER OF NICKEL ADJACENTLY BONDED THERETO WHEREIN SAID UPPER LAYR OF NICKEL IS MORE ANODIC THAN SAID LOWER LAYER OF NICKEL BECAUSE OF THE PRESENCE OF RELATIVELY MORE SULFUR IN SAID UPPER LAYER OF NICKEL THAN IN SAID LOWER LAYER OF NICKEL, SAID METHOD COMPRISING ELECTRODEPOSITING UPON A METAL BODY SAID LOWER LAYER OF NICKEL FROM AN AQUEOUS ACID BATH MAINTAINED AT A PH BETWEEN 2 AND 4 CONTAINING A NICKEL-SUPPLYING COMPOUND AND A SULFUR-SUPPLYING COMPOUND AT A CURRENT DENSITY IN THE RANGE OF FROM ABOUT 40 AMPERES PER SQUARE FOOT TO ABOUT 150 AMPERES PER SQUARE FOOT AND AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 100*F. TO ABOUT 165*F., AND WHEREIN THE POTENTIAL OF SAID DEPOSIT IS DETERMINED IN AN ELECTROLYTE COMPRISING AN AQUEOUS SOLUTION OF 3 GRAMS OF SODIUM CHLORIDE AND .02 GRAM OF CU(NO3)3.3H2O PER 100 MLS. OF WATER ADJUSTED TO A PH OF 3.0 AND AT ROOM TEMPERATURE; AND DEPOSITING SAID UPPER LAYER OF NICKEL UPON SAID LOWER LAYER OF NICKEL FROM A SIMILAR BATH CONTAINING A BRIGHTENER COMPOUND WHEREIN SAID DEPOSIT HAS A POTENTIAL AS MEASURED OF AT LEAST 60 MILLIVOLTS MORE ANODIC THAN SAID LOWER LAYER OF NICKEL.
 10. A CORROSION RESISTANT ARTICLE COMPRISING A BASIS METAL OF THE TYPE WHICH IS SUBJECT TO ATMOSPHERIC CORROSION COATED WITH TWO SUPERIMPOSED COATES OF SULFUR CONTAINING NICKEL, SAID NICKEL COATINGS CONTAINING DIFFERENT AMOUNTS OF SULFUR SUCH THAT THE TOP NICKEL LAYER IS NOT LESS THAN 60 MV. MORE ELECTRONEGATIVE THAN THE UNDERLYING NICKEL LAYER, SAID ELECTRONEGATIVITY BEING DETERMINED FROM POTENTIAL MEASUREMENTS TAKEN IN A SOLUTION OF 3 G. OF NACL AND .02 G. OF CU(NO3)5.3H2O PER 100 MLS. OF WATER AT A PH OF 3.0 AT ROOM TEMPERATURE. 